Assessment of Dual-Cure Resin Cement Properties of Microhardness and Water Sorption/Solubility through Various Shades of Monolithic Zirconia

Background: It is important to evaluate the physical properties of dual-cure resin cement in different shades of monolithic zirconia because such an understanding is necessary for its clinical application. Materials and Methods: For this in vitro study, 60 specimens of dual-cure resin cement were prepared and grouped into three sets (n = 20) according to monolithic zirconia shade: light, medium, and dark. Two-millimeter-thick discs of each shade were used as substrates for curing the resin cement. A Vickers hardness tester was employed for measuring microhardness, while ISO 4049 standards were followed for examining water sorption and solubility. Measurements were recorded at 24 hours, baseline, and 1 week after curing. Results: The highest mean value of microhardness (85 HV) was observed in the light shade zirconia group, whereas medium and dark shades exhibited average values equal to 80 HV and 75 HV, respectively. The dark shade showed maximum water sorption among other groups with a mean value of 35 μg/mm³, followed by medium (30 μg/mm3) and light (25 μg/mm3) shades. In relation to solubility, the dark shade also had the highest value, which was approximately 3.5 μ/mm3, while the medium shade showed around 2.5 μg/mm3 and the light shade exhibited nearly 1.5 μg/mm3. Conclusion: Microhardness and water sorption/solubility are significantly affected by the shade variation of monolithic zirconias combined with dual-cured resins. Lighter shades result in higher microhardness and lower water absorption and solubility, leading to better performance and longer lifespan.